Linking with f77-Compiled Routines

• To mix f77 and f90 object binaries, link with f90 and the f77 compatibility library, libf77compat, and not with libF77. For example, perform the link step with

  f90 ..files.. -lf77compat

  even if the main program is an f77 program.

  Example: f90 main and f77 subroutine.

  ---

  demo% cat m.f90
  CHARACTER*74 :: c = 'This is a test.'
     CALL echo1( c )
  END
  demo$ cat s.f
         SUBROUTINE echo1( a )
         CHARACTER*74 a
         PRINT*, a
         RETURN
         END
  demo% f77 -c -silent s.f
  demo% f90 m.f90 s.o -lf77compat
  demo% a.out
   This is a test.
  demo% 

  ---

• The FORTRAN 77 library is generally compatible with f90.

Example: f90 main calls a routine from the FORTRAN 77 library.

demo% cat tdtime.f90
        REAL e, dtime, t(2)
        e = dtime( t )
        DO i = 1, 100000
           as = as + cos(sqrt(float(i)))
        END DO
        e = dtime( t )
        PRINT *, 'elapsed:', e, ', user:', t(1), ', sys:', t(2)
        END
demo% f90 tdtime.f90
demo% a.out
elapsed: 0.14 , user: 0.14 , sys: 0.0E+0
demo% 

See dtime(3F).